Jeremy Corbyn has just a month to back down over the anti-Semitism row or face losing the backing of allies in Momentum and a major trade union, it today emerged.

Labour has been plunged into a bitter civil war over how to tackle the racist abuse which has festered among some of its members.

The Labour leader has rebuffed demands by Jewish leaders and many of his own MPs to fully adopt the international definition of anti-Semitism - a move they insist is crucial if the party is to finally get on top of the scandal.

The party has adopted some of the International Holocaust Remembrance Alliance's definition, but crucially it has not included several of the examples they use to illustrate it - including that Israel's existence as a state is a racist endeavor.

But he has now been told by his powerful allies he must formally sign up to the definition at a crunch party meeting in early September, the Politico website reports.

Activists have given the ultimatum amid fears the scandal is ripping the party apart and could cost the party their chances of winning the next election.

The Labour leader (pictured outside his Islington home on Monday) has rebuffed demands by Jewish leaders and many of his own MPs to fully adopt the international definition of anti-Semitism - a move they insist is crucial if the party is to finally get on top of the scandal

In an angry diatribe at a meeting of Labour's ruling executive committee, he said he was 'amazed' there was evidence party members hated Jews.

He claimed 'some of these people in the Jewish community support Trump – they are Trump fanatics' before shouting: 'So I am not going to be lectured to by Trump fanatics making up duff information without any evidence at all.'

August 2018:

Jeremy Corbyn issues a video insisting he is committed to tackling the racism - but it is panned by Jewish leaders.

Corbynistas mount a social media campaign to get deputy Labour leader Tom Watson to quit after he criticises the party's handling of anti-Semitism.

The Daily Mail exclusively publishes photos of Jeremy Corbyn holding a wreath at a ceremony where a terrorist linked to the Munich massacre was honoured.

The Labour leader insists he was there to honour others killed - but faces fresh calls to quit over the scandal.

Jon Lansman, head of Momentum - the grassroots activist group set up to elect keep Mr Corbyn in power - has been lobbying the Labour leader to accept the definition.

A senior Labour official told Politico: 'That it has come to this is a total disaster. It could cost the Labour party the next election.'

The party's ruling National Executive Committee will hod a crunch meeting on September 4, where the showdown will come to a final head.

Momentum and one of Mr Corbyn's major trade union backers are insisting the party leadership signs up to the International Holocaust Remembrance Alliance (IHRA) definition of anti-Semitism there.

It comes a day before Labour MPs are meeting on September 5, when they are expected to back the definition.

Labour has been dogged by accusations of anti-Semitism ever since Mr Corbyn was elected in 2015.

Labour MPs have told how they have been met with a wave of anti-Semitic vitriol, death and rape threats after they dared to speak out about the racism.

And they have furiously torn into their leader for willfully ignoring the racism festering among some of his supporters.

But the latest row has reignited after the Labour leadership refused to fully accept the international anti-Semitism definition.

Mr Corbyn's office sparked fresh anger after it launched formal investigations into two Labour MPs, Dame Margaret Hodge and Ian Austin - who both lost family in the Holocaust - after they rowed with party bosses about the failure to tackle the abuse.

The probe into Dame Margaret has been dropped but Mr Austin remains under formal investigation.

A senior figure close to Mr Corbyn said: 'My view now is we are going to move, significantly, making the concession, with all of the examples. I'm confident that we will. It's a matter of the choreography.'

The official said that they have realised that they have no chance of winning back the trust of the Jewish community unless they make the concession.

They said: 'It's about trust, not about textual examples. I think it [the definition] has got lots of flaws — the definition itself is poorly worded.

'But for the Jewish community it clearly has become totemic. When there is a lack of trust, you have got to get over that.

'Politically it's necessary to do what it takes. In my view, this situation is allowing real anti-Semites to act with impunity. We can't allow that to happen.'

Meanwhile, Jewish news reports that Mr Lansman has been lobbying the leadership directly.

A source said: 'Like many other leading party members close to the leadership, he recognises the necessity of agreeing that definition in order to be able to begin to rebuild trust with the Jewish community, whatever concerns we may have about the application of some examples.'

International holocaust experts earlier this week accused the Labour party of undermining efforts to stamp out anti-Semitism by not accepting the definition.

The International Holocaust Remembrance Alliance said the party's high controversial decision to refuse to fully adopt is definition of anti-Semitism was hampering efforts.

In their first intervention since the row erupted last month about Labour's refusal to take up the definition last month, they criticised Labour for excluding some of the specific examples of the racism.

They stressed the importance of a global definition of anti-semitism to any effort to tackle it.

And they said that by picking and choosing what bits o the definition to use, the party is hampering efforts to actually tackle the abuse.

They add: 'Any ‘modified’ version of the IHRA definition that does not include all of its 11 examples is no longer the IHRA definition.

'Adding or removing language undermines the months of international diplomacy and academic rigour that enabled this definition to exist.

'If one organisation or institution can amend the wording to suit its own needs, then logically anyone else could do the same.

'We would once again revert to a world where antisemitism goes unaddressed simply because different entities cannot agree on what it is.'

Jon Lansman (pictured), head of Momentum - the grassroots activist group set up to elect keep Mr Corbyn in power - has been lobbying the Labour leader to accept the definition.